不同铸坯组织对nb、v、ti微合金钢直接送装裂纹影响的实验分析

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1、重庆大学硕士学位论文II英文摘要ABSTRACTContinuouscastingslabsprovidedfromcasterwithoutcoolingthenchargedirectlytoheatingfurnaceusuallynameddirectcharge,whichcansaveenergy.ButforNb,VandTicontainingsteel,crackusuallycanbefoundonfinalproductsurfaceafterdirectcharge-rolling.Thosecracksdecreasedd

2、irectchargepercentageofmicroalloyedsteelsignificantly.Tosolvethisproblem,weconductedbelowresearchestorevealspecificmechanismofmicroalloyedsteeldirectcharge:1.Whenandhowthecrackformedinmicroalloyedsteeldirectcharge2.Effectofmicrostructureonrelatedcrackformation.3.Howthecrackcan

3、beavoidedthroughprocessoptimization.Researchmethod:ChooseE36steelasresearchobjectandQ235ascomparison.First,weperformedheattreatmentonsamplesintubefurnace.Thewholeprocesswasasfaraspossibletosimulatedirectcharge.Thenweanalyzeditsmicrostructurewithopticalmicroscope,SEMandTEMtorev

4、ealtheinformationofmicrostructure,cracksandprecipitates.Throughlabexperiments,someconcludescanbeformed:Thecracksformedfromcharginginheatfurnacearound700℃tillheatingto800℃（Ac3）,inthis100℃section,experimentalsampleswereinferrite-austenitecoexistzone.α→γchangecausehugetensilestre

5、ss,Nb、V、Ticontainingparticipatesincreasedtoitsmaximumquantityat800℃.Reheatingsamplesto1200℃withdifferentchargingmircostructure:Nocrackswerefoundinpearliteandlowerbainitemicrostructuresamples.Butforgranularbainite,upperbainiteandmartensitesamples,crackswereformedbecauseofprecip

6、itatesandhardness.Featureofprecipitatesunderdifferentmicrostructures:1.Inpearlite:largequantityofprecipitatesbutsingleoneissmallandwithhomogeneousdistribution.2.Ingranularbainiteandupperbainite:withlittlequantityofprecipitatesbuteasytogatherongrainboundary.3.Inlowerbainiteandm

7、artensite:extremelylowquantityofprecipitates.Carbonitrideofmicroalloyelementprecipitates:1.SolubilityofcarbonitrideofmicroalloyelementindifferentmicrostructureisIII重庆大学硕士学位论文notthesame.Thisphenomenonaffectsthedistributionofprecipitates.2.Highcoolingspeedwilldecreasethesizeofpr

8、ecipitates.Thiswillaffectthequantityofprecipitates.Austenite,